Mitosis & Meiosis

Key Vocab Chromosome- long thread of DNA that consists of many genes Humans have 46 chromosomes (23 pairs) Gametes- sex cells such as egg and sperm (meiosis) Somatic cells- body cells (mitosis) Homologous chromosomes- two chromosomes; one from mom and other from dad Diploid- a cell has two copies of each chromosome (cells at end of mitosis) (46) Haploid- a cell has only one copy of each chromosome (cells at end of meiosis) (23) Sexual reproduction- type of reproduction that requires 2 parents ( an egg and a sperm) to produce offspring (young/baby) Asexual Reproduction- Type of reproduction needing only ONE single parent. Offspring is Identical to the parent. No genetic variation. Cloning.

Mitosis Uses: growth, cell replacement, healing and repair Asexual reproduction: one parent produces offspring that are identical to parent Cell division- one cell separates into two cells Each new cell contains the SAME amount of chromosomes as the original cell The DNA is copied before the cell divides One copy of the genetic information is distributed to each new daughter cell

Process of Mitosis DNA REPLICATES- DOUBLES Double-stranded chromosomes (replicated) line up at the center of the cell before division. Double-stranded chromosomes split into 2 identical single strands and move toward opposite ends of the cell The cytoplasm divides resulting in two smaller, but genetically identical cells Cells are diploid at beginning and end of mitosis

Phases of Mitosis

Microscopic View of Mitosis

Cancer Uncontrolled cellular division. Cancerous cells keep dividing; crowding out and stealing nutrients from healthy tissue. Cancer “kills” when a mass of cancer cells called a tumor interferes with the functions of major organs. The spreading of cancer to other organs and tissues is known as metastasis. Tumor

Asexual Reproduction One parent No genetic variation Identical to parent Offspring has the same # of chromosomes as parent RESULTS IN 2 IDENTICAL Cells

Types of Asexual Reproduction MITOSIS BINARY FISSION BUDDING VEGETATIVE PROPAGATION SPORULATION REGENERATION

Binary Fission- EQUAL DIVISION --Examples: bacteria, amoeba, paramecium

Budding- a cell of a parent develops a bud Budding- a cell of a parent develops a bud. - Uneven division Examples: yeast, hydra

Sporulation- each spore contains DNA Sporulation- each spore contains DNA --each spore can develop into a new organism --Examples: Bread Mold

Regeneration- Replacement of lost or damaged body parts Examples: lobster, starfish, planaria, some reptiles

Vegetative Propagation- new plant develops from part of a parent plant Examples: onion, potato, tulip

Let’s Practice! 1. The diagrams represent a cell process. If the cell in Diagram 1 contains 4 chromosomes, what is the total number of chromosomes in each cell in Diagram 3? 8 2 16 4

2. Which process is represented by the series of diagrams? photosynthesis fertilization mitotic cell division meiotic cell division

3. Normal mitotic cell division results in each daughter cell having half the number of chromosomes as the parent cell the same number and kinds of chromosomes as the parent cell the same number but different kinds of chromosomes as the parent cell twice the number of chromosomes as the parent cell

4. A colony of red bacteria is allowed to reproduce for 16 generations 4. A colony of red bacteria is allowed to reproduce for 16 generations.  A scientist examines the colony at the end of this time and notes that all the individuals are almost identical in all characteristics.  This evidence suggests that the bacteria did not receive the proper nutrients reproduced sexually exchanged genetic material reproduced asexually

5. Which phrases best identify characteristics of asexual reproduction? one parent, union of gametes, offspring similar to but not genetically identical to the parent one parent, no union of gametes, offspring genetically identical to parents two parents, union of gametes, offspring similar to but not genetically identical to parents two parents, no union of gametes, offspring genetically identical to parents

6. Which activity most directly involves the process represented in the diagram below? a gamete reproducing sexually a white blood cell engulfing bacteria a zygote being produced in an ovary an animal repairing damaged tissue

7. Which statement regarding this process is correct? Cell B contains the same genetic information that cells A and C contain. Cell C has DNA that is only 50% identical to cell B. Cell A has DNA that is only 75% identical to cell B. Cells A, B, and C contain completely different genetic information.

8. The diagram can be used to illustrate a process directly involved in tissue repair meiosis cellular respiration sexual reproduction

9. Warts result when certain viruses cause skin cells to reproduce at a high rate. This rapid reproduction of skin cells is due to the viruses stimulating cellular digestion  mitotic cell division  synthesis processes meiotic cell division

Meiosis Sexual reproduction Occurs in gametes or sex cells (eggs and sperm) ONLY Meiosis produces haploid cells that have one half the chromosomes of the original cell Gametes or sex cells (sperm/eggs) have one half the amount of chromosomes as the original cell

Phases of Meiosis First Phase of Meiotic Division- double stranded chromosomes line up in pairs in the center and then divide into two cells Second Phase of Meiotic Division- division of the two newly formed cells Each chromosome in the two cells still consists of two strands that will separate resulting in 4 cells

Phases of Meiosis

Meiosis in Testes of Males

Meiosis in Ovaries of Females Egg Cell (Nonfunctioning Cells)

Meiosis Comparison

Meiosis: Source of Variation During meiosis, genetic variation occurs. Sources of Variation Crossing over Genetic Recombination- during fertilization (Egg and Sperm) Random fertilization of Gametes-

1. Crossing Over- Random exchange of chromosome pieces (genetic information between chromosomes)

2. Genetic Recombination- during fertilization (Egg and Sperm) 2. Genetic Recombination- during fertilization (Egg and Sperm) --Different combinations of chromosomes can be produced (about 8 million different combinations)

Random Fertilization of Gametes- random combination of gametes or egg and sperm --About 70 trillion possible combinations of the egg and sperm

Mitosis Meiosis Produces 2 genetically identical cells Produces 4 genetically unique/ different cells Results in diploid cells Results in haploid cells Takes place in body cells or somatic cells only Takes place only in sex cells or gametes Sperm and egg Involved in asexual reproduction Involved in sexual reproduction

Let’s Practice! 1. Each body cell of a chimpanzee contains 48 chromosomes. How many chromosomes would normally be present in a gamete produced by this chimpanzee? 24 36 48 96

2. Which process is represented by the diagram? fertilization production of gametes cloning evolution

3. The process of meiotic cell division in a human male usually forms one diploid cell, only four diploid cells one monoploid cell, only four monoploid cells

4. Cell with a diploid chromosome number of 12 divided two times, producing four cells with six chromosomes each. The process that produced these four cells was most likely internal fertilization external fertilization mitotic cell division meiotic cell division

5. Most cells in the body of a fruit fly contain eight chromosomes 5. Most cells in the body of a fruit fly contain eight chromosomes.  How many of these chromosomes were contributed by each parent of the fruit fly? 8 2 16 4

6. Which diagram best represents part of the process of sperm formation in an organism that has a normal chromosome number of eight? 1. 3. 2. 4.

7. The diagram below shows a process that can occur during meiosis 7. The diagram below shows a process that can occur during meiosis. The most likely result of this process is a new combination of inheritable traits that can appear in the offspring an inability to pass either of these chromosomes on to offspring a loss of genetic information that will produce a genetic disorder in the offspring an increase in the chromosome number of the organism in which this process occurs

8. A particular species of shark normally reproduces sexually 8. A particular species of shark normally reproduces sexually. In captivity, it was found that a female could also reproduce asexually. One negative result from asexual reproduction is increased gene recombinations increased number of males produced decreased number of eggs used decreased biodiversity within the species

References http://www.tokresource.org/tok_classes/biobiobio/biomenu/index.htm McDougal Littell Biology Living Environment Textbook